Bucks Diary

Sunday, April 20, 2008

Odds lengthen for yesterday's NBA playoff losers


I've been down with a flu bug for the last couple of days. A perfect excuse for an afternoon of non-stop NBA action. Yesterday I put in 11 hours of "the best in basketball" and Vitamin C. Hoopsters heaven. Mostly close games, but nevertheless, the odds of getting out of the first round for yesterday's losers have gotten a bit longer.

Using Cook's method to calculate playoff odds

Prior to the playoffs, I calculated each playoff team's home and road "efficiency differentials", split them, then used this formula to determine each team's overall expected winning percentage, then plugged those numbers into the "seven game series" formula developed by Professor Earnshaw Cook to evaluate the World Series in his classic book "Percentage Baseball". I then charted the results and called them the odds of each team getting out of the first round. (Note: I miscalculated one of the series. I thought Utah was the home team, and thus calculated their chances of getting out of Round 1 at 56.2%. However, they are the road team. Still though, they were the favorite to win going into the series, with their odds of winning being 51.4%.)

After Saturday's results, I recalculated the odds. Click here to see my new results.

As you can see, even though most NBA analysts view NBA series as tennis matches (in that they often say the winning team-- if it holds home court advantage-- has merely "held serve") the fact is that any loss in a playoff series greatly lengthens the odds that the loser will end up winning the series.

That's because the tennis analogy doesn't really hold. In tennis, the initial returner gets just as many opportunities to serve as the initial server. By contrast, in the basketball playoffs the team with home court advantage gets one extra "serve" than its opponent. And more importantly, "games" won in tennis are not equivalent to "games" won in basketball. A basketball victory is more analagous to winning a "set" in tennis.

After winning a set in tennis or a game in a basketball playoff series, the winner, in contrast to the loser, is placed in a position where it now needs to win fewer victories in the same number of contests. Given this new "advantage", the victors odds of ultimate victory increase substantially.

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